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Figure 1 | Breast Cancer Research

Figure 1

From: Tumour-associated carbohydrate antigens in breast cancer

Figure 1

Pathways of biosynthesis of O -glycans in normal and cancer breast epithelial cells. All of these transfer reactions are catalysed in the Golgi apparatus. Enzymes involved in the pathways are indicated in italic font next to the arrows. Various mechanisms are illustrated by which O-glycans expressed in normal cells (bottom left) can be turned down to shorter and sialylated species. First, the enzymes involved in extended O-glycans can be downregulated or mutated (downward white arrows) in cancer cells, leading to a decrease or an absence of extended structures and revealing previously masked precursors such as T and Tn antigens. Alternatively or concomitantly, overexpression of diverse sialyltransferases (upward white arrows) can compete with the enzymes of normal extension and generate truncated sialylated structures (right column). This competition can occur at different levels of the extension pathway and produce the sialylated structures of each precursor (that is, sialyl-Thomsen-nouvelle (sTn) antigen, sialyl-Thomsen-Friedenreich (sialyl-T or sialyl-TF) antigen (or sialylated Core1) and sialylated Core2 O-glycans). Gal, Galactose, GalNAc, N-acetylgalactosamine; GlcNAc, N-acetylglucosamine; Neu5Ac, N-acetylneuraminic acid; Fuc, fucose. Linkages (anomery and carbons involved) are only indicated the first time they appear along the pathway. N, various numbers (2 to 10) of repeats of lactosamine units (Gal β1-3/4GlcNAc).

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